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Thread: MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures
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Old 10th Oct 2019, 18:01
  #3002 (permalink)  
Tomaski
 
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Originally Posted by safetypee

Speed trim failure - new ? How engineered.
Stab out of trim; very interesting, how determined.
No MCAS ‘FAIL’ (inhibited) annunciation ?
  • Speed Trim failure is not new and has an associated annunciator on the overhead panel. Loss of Speed Trim is not a serious issue.
  • Stab Out of Trim is an annunciated malfunction that occurs when there is excess elevator displacement with the autopilot engaged. Also not new. This occurs when the A/P is unable (or slow) to trim the stabilizer. However, the current NNC procedures for Stab Out of Trim would actually delay the appropriate response if this occurs as a result of a Stab Trim Runaway with A/P engaged.
  • MCAS is a sub-function of Speed Trim, so presumably a MCAS inop malfunction will be indicated by the existing "Speed Trim" annunciator. Loss of MCAS would also not be a serious issue as long as the pilots maintained vigilance in regard to avoiding high-AOA situations.
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